In today's dynamic business environment, accounting entrepreneurs must demonstrate both entrepreneurial competencies and strong ethical conduct to achieve sustainable success. This study examines how these two factors influence the performance of small accounting practices in Thailand. Employing a convergent parallel mixed-methods design, the research integrates quantitative data from 400 accounting firm owners and qualitative insights from 10 semi-structured interviews. Guided by an integrated conceptual model, the study tested three hypotheses: (H1) the direct effects of entrepreneurial competency and ethical conduct on practice success; (H2) the mediating role of entrepreneurial competency in translating professional skills into performance; and (H3) a sequential mediation path from professional skills through ethical conduct and entrepreneurial competency to success. Quantitative results confirmed that both entrepreneurial competency and ethical conduct significantly predicted practice success (p < 0.01). Mediation analysis supported H2 and H3, showing that entrepreneurial competency acts as a key mechanism linking technical and ethical qualities to performance outcomes. The qualitative findings enriched these results, revealing how successful practitioners emphasize integrity, transparent client relationships, adaptability, and continuous learning in practice. The study highlights the interdependence between ethics and entrepreneurship and underscores the need for accounting education and professional development to integrate these competencies. Implications are discussed for curriculum reform, continuing professional education, and policy alignment in Thailand's accounting sector. By fostering ethically grounded entrepreneurial mindsets, stakeholders can better equip accounting professionals to navigate complexity and drive sustainable growth.